JP2005351120A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure request torque; and to restrain a change in an inside EGR quantity, while performing negative pressure control for securing intake pipe negative pressure, in a system for performing intake air quantity control by variable intake valve control. <P>SOLUTION: Target intake pipe pressure MPM is calculated in response to an item of a negative pressure request, and throttle opening is controlled so as to realize this target intake pipe pressure MPM, and required intake pipe negative pressure is secured. A target intake air quantity MGA is calculated on the basis of accelerator opening, and the intake valve closing timing is controlled so as to realize this target intake air quantity MGA, and the request torque is secured. A target inside EGR correction quantity MEGR is calculated on the basis of the target intake air quantity MGA and the target intake pipe pressure MPM, and the intake valve opening timing is controlled so as to realize this target inside EGR correction quantity MEGR, and an inside EGR quantity is decreasingly corrected by an increase quantity of the inside EGR quantity when switched to the negative pressure control from ordinary control, to restrain a change in the inside EGR quantity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for an internal combustion engine provided with a variable valve device capable of controlling an intake air amount by varying valve opening / closing characteristics of both intake valves and intake / exhaust valves of the internal combustion engine.

  In recent years, in an internal combustion engine mounted on a vehicle, for example, as described in Patent Document 1 (Japanese Patent Laid-Open No. 11-117777), a variable intake valve mechanism that varies the lift amount and valve closing timing of the intake valve The intake air amount can be controlled by varying the lift amount and valve closing timing of the intake valve according to the accelerator opening, the engine operating state, and the like. The intake air amount control by the variable intake valve control can reduce the intake air amount without reducing the throttle opening, so that there is an advantage that the pumping loss can be reduced and the fuel consumption can be improved.

  Generally, a vehicle that uses an internal combustion engine as a power source is equipped with a device that uses intake pipe negative pressure generated downstream of a throttle valve. For example, most of the brake boosters that increase the braking force of the brake are negative pressure type brake boosters that use intake pipe negative pressure as a negative pressure source. Further, an evaporative fuel processing device (evaporative gas purge system) that prevents leakage of evaporated fuel (evaporative gas) generated in the fuel tank adsorbs the evaporated fuel generated in the fuel tank to the canister, and the evaporated fuel in the canister The intake pipe is sucked into the intake pipe by negative pressure of the intake pipe. Therefore, in order to operate these negative pressure utilizing devices normally, it is necessary to secure a certain amount of intake pipe negative pressure.

  In the conventional intake air amount control by general throttle valve control, the throttle opening is reduced to reduce the intake air amount at low load, so the intake air pressure downstream of the throttle valve becomes quite negative. In intake air volume control with variable intake valve control, the throttle valve is greatly opened and the intake valve lift amount and valve closing timing are varied to control the amount of air charged in the cylinder. Regardless of this, the intake air pressure downstream of the throttle valve is maintained at almost atmospheric pressure, and the intake pipe required for normal operation of negative pressure equipment such as negative pressure brake boosters and evaporative fuel treatment devices Negative pressure cannot be secured.

Therefore, as described in Patent Document 2 (Japanese Patent Laid-Open No. 2001-173470), when a negative pressure request that requires intake pipe negative pressure is generated, the throttle is set so as to realize the target intake pipe negative pressure. The required intake pipe negative pressure is controlled by controlling the opening and correcting the intake valve closing timing according to the change in intake pipe pressure at that time to correct the intake air amount (in-cylinder charged air amount). There is one that can ensure the required torque while carrying out negative pressure control to ensure the above.
JP-A-11-117777 (second page, etc.) JP 2001-173470 A (second page, etc.)

  However, as in the technique of the above-mentioned Patent Document 2, even when the intake valve closing timing is corrected and the intake air amount is corrected at the time of negative pressure control for securing a necessary intake pipe negative pressure, the change in the intake pipe pressure is changed. Due to this, it is inevitable that the amount of blowback at the time of valve overlap changes and the amount of internal EGR (in-cylinder exhaust gas residual amount) changes, and the influence of this may deteriorate the combustion state.

  The present invention has been made in consideration of such circumstances. Accordingly, the object of the present invention is to ensure the required torque while performing the negative pressure control to ensure the necessary intake pipe negative pressure. Another object of the present invention is to provide a control device for an internal combustion engine that can suppress changes in the internal EGR amount and improve the combustion state during negative pressure control.

  In order to achieve the above object, a control apparatus for an internal combustion engine according to claim 1 of the present invention controls at least an intake air amount by varying valve opening / closing characteristics of intake valves or intake and exhaust valves of the internal combustion engine. In a system including a variable valve device capable of calculating a target intake air amount based on an operating state of the internal combustion engine and / or the vehicle, a target intake air amount calculating means is used, and based on the operating state of the internal combustion engine and / or the vehicle The target intake pipe pressure is calculated by the target intake pipe pressure calculating means, and the target control amount (hereinafter referred to as “target internal EGR control amount”) of the in-cylinder exhaust gas residual amount is set based on the operating state of the internal combustion engine and / or the vehicle. It is calculated by the internal EGR control amount calculation means. Then, the intake air amount is controlled by the intake air amount control means so as to realize the target intake air amount, the intake pipe pressure is controlled by the intake pipe pressure control means so as to realize the target intake pipe pressure, and the target internal EGR control is performed. In-cylinder exhaust gas residual amount (hereinafter referred to as “internal EGR amount”) is controlled by internal EGR amount control means so as to realize the amount.

  In this configuration, when a negative pressure request that requires the intake pipe negative pressure occurs, the required intake air pressure is controlled by controlling the intake pipe pressure so as to achieve the target intake pipe pressure (target intake pipe negative pressure). The negative pressure control for securing the pipe negative pressure can be performed, and the required torque can be secured by controlling the intake air amount so as to realize the target intake air amount. Furthermore, by controlling the internal EGR amount so as to realize the target internal EGR control amount, the change in the internal EGR amount can be suppressed, and the combustion state during negative pressure control can be improved.

  In this case, as in claim 2, the intake air amount is controlled by controlling at least one of the valve closing timing and the lift amount of the intake valve based on the target intake air amount. Good. Since the amount of air that fills the cylinder during the intake stroke changes according to the valve closing timing and lift amount of the intake valve, if the valve closing timing and lift amount of the intake valve are controlled based on the target intake air amount, The amount of air (in-cylinder charged air amount) can be controlled to the target intake air amount.

  Further, as in claim 3, the intake pipe pressure is preferably controlled by controlling the throttle opening based on the target intake pipe pressure. Since the intake pipe pressure changes according to the throttle opening, the intake pipe pressure can be controlled to the target intake pipe pressure by controlling the throttle opening based on the target intake pipe pressure.

  Further, according to the fourth aspect of the invention, the internal EGR amount is controlled by controlling at least one of the valve opening timing and the valve overlap amount of the intake valve based on the target internal EGR control amount. It is good to do so. Since there is a characteristic that the amount of blowback at the time of valve overlap changes and the amount of internal EGR changes according to the valve opening timing and valve overlap amount of the intake valve, the valve opening of the intake valve is based on the target internal EGR control amount. By controlling the timing and valve overlap amount, the target internal EGR control amount can be realized.

  Further, as in claim 5, when a negative pressure request that requires an intake pipe negative pressure is generated, the target intake pipe pressure may be calculated according to the negative pressure request item. In this way, an appropriate target intake pipe pressure (target intake pipe negative pressure) is set for each negative pressure request item (eg, brake negative pressure request, purge control negative pressure request, etc.). Thus, the necessary negative pressure of the intake pipe can be ensured and the intake pipe pressure can be prevented from becoming more negative than necessary. Increase in the amount of EGR) can be prevented.

  Further, as in claim 6, when the target intake pipe pressure is set to a predetermined negative pressure, the target intake air amount is set so that the intake air amount is equivalent to that during normal control. good. In this way, even during negative pressure control, an intake air amount equivalent to that during normal control can be secured, and torque equivalent to that during normal control can be secured.

  Further, as in claim 7, it is preferable to set the target internal EGR control amount so that the internal EGR amount is equal to that during normal control during negative pressure control. In this way, even during negative pressure control, an internal EGR amount equivalent to that during normal control can be ensured, and a combustion state equivalent to that during normal control can be ensured.

  By the way, during negative pressure control, there is a tendency for the amount of blowback at the time of valve overlap to increase due to a decrease in intake pipe pressure, and as a result, the amount of wet fuel adhering to the inner wall of the intake port and the like increases. There is a concern that the amount of fuel supplied to the engine will decrease and the air-fuel ratio will be disturbed.

  Therefore, as in claim 8, the fuel injection amount may be corrected according to the actual intake pipe pressure during negative pressure control. In this way, the change in the amount of fuel supplied to the cylinder by correcting the fuel injection amount in response to the change in the wet amount in accordance with the intake pipe pressure (intake pipe negative pressure) during negative pressure control. It is possible to prevent the air-fuel ratio from being disturbed during negative pressure control.

  Further, as in claim 9, when the combustion state deteriorates during negative pressure control, the target internal EGR control amount and / or the target intake pipe pressure may be corrected so that the combustion state is improved. good. In this way, it is possible to prevent deterioration of drivability during negative pressure control.

  In general, if the internal EGR amount becomes too large, the combustion state deteriorates. Therefore, as in claim 10, when the combustion state deteriorates during negative pressure control, the target internal EGR control is performed in a direction in which the internal EGR amount is reduced. It is better to correct the amount. In this way, if the combustion state deteriorates during negative pressure control, the internal EGR amount can be reduced to improve the combustion state.

  Further, as the intake pipe pressure approaches the atmospheric pressure, the amount of blow-back at the time of valve overlap tends to decrease and the amount of internal EGR tends to decrease, so the combustion state deteriorates during negative pressure control as in claim 11. In this case, the target intake pipe pressure may be corrected so as to approach the atmospheric pressure. In this way, when the combustion state deteriorates during negative pressure control, the internal intake gas pressure can be corrected so as to approach the atmospheric pressure, thereby reducing the internal EGR amount and improving the combustion state.

  Hereinafter, the best mode for carrying out the present invention will be described using the following two Examples 1 and 2.

A first embodiment of the present invention will be described with reference to FIGS.
First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. On the downstream side of the air flow meter 14, a throttle valve 16 whose opening is adjusted by an electric actuator 15 such as a motor, and a throttle opening sensor (not shown) for detecting the throttle opening are provided. .

  Further, a surge tank 17 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 18 for detecting the intake pipe pressure is provided in the surge tank 17. The surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 19 of each cylinder. Yes. A spark plug 21 is attached to each cylinder of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each spark plug 21.

  The intake valve 28 and the exhaust valve 29 of the engine 11 are electromagnetically driven valves that are driven by electromagnetic actuators 30 and 31 (variable valve devices), respectively. The intake valve 28 and the exhaust valve 29 are driven by these electromagnetic actuators 30 and 31. The valve opening timing and valve closing timing can be arbitrarily changed.

  On the other hand, the exhaust pipe 22 of the engine 11 is provided with a catalyst 23 such as a three-way catalyst for purifying CO, HC, NOx and the like in the exhaust gas, and the exhaust gas on the upstream side and the downstream side of the catalyst 23 respectively. An exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting air-fuel ratio or rich / lean is provided.

  A cooling water temperature sensor 25 that detects the cooling water temperature and a crank angle sensor 26 that outputs a pulse signal each time the crankshaft of the engine 11 rotates a predetermined crank angle are attached to the cylinder block of the engine 11. Based on the output signal of the crank angle sensor 26, the crank angle and the engine speed are detected.

  Further, the evaporated fuel (evaporative gas) generated by evaporating the fuel in the fuel tank 32 is adsorbed by an adsorbent (not shown) such as activated carbon in the canister 34 through the communication pipe 33. A purge pipe 35 is connected between the canister 34 and the intake pipe 12 on the downstream side of the throttle valve 16 to suck the evaporated fuel adsorbed in the canister 34 into the intake pipe 12. A purge control valve 36 for adjusting the fuel vapor purge amount is provided in the middle of the process. The canister 34, the purge pipe 35, the purge control valve 36, and the like constitute an evaporated fuel processing device 37. Note that the purge pipe 35 may be connected to the surge tank 17.

  A brake booster 39 is connected to the surge tank 17 via a negative pressure introduction pipe 38. The negative pressure introduction pipe 38 may be connected to the intake pipe 12 between the throttle valve 16 and the surge tank 17.

  Outputs of the various sensors described above are input to an engine control circuit (hereinafter referred to as “ECU”) 27. The ECU 27 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount of the fuel injection valve 20 according to the engine operating state. The ignition timing of the spark plug 21 is controlled.

  In addition, the ECU 27 controls the electromagnetic actuator 30 according to the target intake air amount set based on the accelerator opening and the like, and varies the valve closing timing of the intake valve 28 to control the intake air amount.

  In the intake air amount control based on such variable intake valve control, the pumping loss is reduced by controlling the charge air amount in the cylinder by varying the closing timing of the intake valve 28 while the throttle valve 16 is largely opened. Since the fuel efficiency is improved by reducing the pressure, the pressure in the intake pipe 12 on the downstream side of the throttle valve 16 can be maintained at almost atmospheric pressure regardless of whether the load is low or high. The intake pipe negative pressure necessary for normal operation of the device using the negative pressure such as the evaporative fuel processing device 37 cannot be secured.

  Therefore, the ECU 27 executes the programs shown in FIGS. 2 to 10 to perform the negative pressure control for securing the necessary intake pipe negative pressure as follows.

  First, when a negative pressure request that requires intake pipe negative pressure is generated, the target is determined according to the negative pressure request items (for example, negative pressure demand for brake, negative pressure demand for purge control, etc.) An intake pipe pressure MPM (target intake pipe negative pressure) is calculated, and a target throttle opening degree that realizes the target intake pipe pressure MPM is calculated. The throttle valve 16 (actuator 15) is controlled so that the actual throttle opening coincides with the target throttle opening, and the actual intake pipe pressure is controlled to the target intake pipe pressure MPM. Secure.

  Further, a target intake air amount MGA is calculated based on the accelerator opening, the vehicle speed, and the like, and a target intake valve closing timing for realizing the target intake air amount MGA is calculated. Then, by controlling the electromagnetic actuator 30 so that the actual intake valve closing timing coincides with the target intake valve closing timing, the actual intake air amount (actual cylinder charge air amount) is controlled to the target intake air amount MGA. Thus, the required torque according to the accelerator opening is secured.

Further, the internal EGR amount EGR1 during normal control is calculated based on the target intake air amount MGA and the operating state of the engine 11 and the vehicle, and negative based on the target intake pipe pressure MPM and the operating state of the engine 11 and the vehicle. After calculating the internal EGR amount EGR2 during pressure control, the difference between the internal EGR amount EGR2 during negative pressure control and the internal EGR amount EGR1 during normal control (that is, the internal EGR amount when switching from normal control to negative pressure control) And the target internal EGR correction amount MEGR.
MEGR = EGR2-EGR1

The target correction amount of the intake valve opening timing (or valve overlap amount) for reducing the internal EGR amount by this target internal EGR correction amount MEGR is calculated, and the current intake valve opening timing (or valve overlap amount) is targeted. The electromagnetic actuator 30 is controlled so that only the correction amount is corrected, and the change in the internal EGR amount is suppressed by correcting the decrease in the internal EGR amount by the increase in the internal EGR amount when switching from the normal control to the negative pressure control. Thus, the combustion state during negative pressure control is improved.
The processing contents of the programs shown in FIGS. 2 to 10 executed by the ECU 27 will be described below.

[Negative pressure request judgment]
The negative pressure request determination program shown in FIG. 2 is executed at a predetermined cycle during engine operation. When this program is started, first, in step 101, the operating state of the engine 11 and the vehicle (for example, the coolant temperature, etc.) is read. Thereafter, the process proceeds to step 102, where it is determined whether the catalyst warm-up control is being performed (for example, the coolant temperature is equal to or lower than a predetermined value) or whether the elapsed time after startup is less than a predetermined time (for example, 20 seconds).

  As a result, when it is determined that the catalyst warm-up control is being performed, or when it is determined that the elapsed time after the start is less than the predetermined time, the process proceeds to step 103 and the catalyst 23 is warmed up (active state). ) Is estimated based on the output of the exhaust gas sensor 24, for example.

  Thereafter, the routine proceeds to step 104, where it is determined whether or not the catalyst 23 is inactive based on the estimation result of the warm-up state of the catalyst 23. As a result, if it is determined that the catalyst 23 is inactive, the routine proceeds to step 105, where the negative pressure request flag XFUATU is set to “1” which means a negative pressure request for starting (when the catalyst is inactive). Set and exit this program.

  On the other hand, if it is determined in step 102 that the catalyst warm-up control is not being performed and it is determined that the elapsed time after start exceeds a predetermined time, or in step 104, the catalyst 23 is in an active state. If it is determined that there is, the routine proceeds to step 106, where it is determined whether or not the pressure in the brake booster 39 is higher than a predetermined value.

  As a result, when it is determined that the pressure in the brake booster 39 is higher than the predetermined value, the routine proceeds to step 107, where the negative pressure request flag XFUATU is set to “2” meaning a negative pressure request for brake. End this program.

  On the other hand, if it is determined in step 106 that the pressure in the brake booster 39 is equal to or lower than the predetermined value, the process proceeds to step 108 and the evaporated fuel adsorbed in the canister 32 is sucked into the intake pipe 12. It is determined whether there is a request for purge control.

  As a result, if it is determined that there is a purge control request, the process proceeds to step 109, the negative pressure request flag XFUATU is set to “3” meaning a negative pressure request for purge control, and this program is terminated. To do.

  On the other hand, if it is determined in step 108 that there is no purge control request, the process proceeds to step 110 to determine whether there is another negative pressure request (for example, for failure diagnosis). As a result, if it is determined that there is another negative pressure request, the process proceeds to step 111, the negative pressure request flag XFUATU is set to “4” indicating another negative pressure request, and this program is terminated. To do.

  On the other hand, if it is determined in step 110 that there is no other negative pressure request, the process proceeds to step 112 where the negative pressure request flag XFUATU is reset to “0” meaning no negative pressure is requested. Exit the program.

[Negative pressure control]
The negative pressure control program shown in FIG. 3 is executed at a predetermined cycle during engine operation. When this program is started, first, in step 201, the operating state of the engine 11 and the vehicle (for example, engine rotation speed, accelerator opening, vehicle speed, etc.) is read.

  Thereafter, the routine proceeds to step 202, where it is determined whether or not there is a negative pressure request depending on whether or not the negative pressure request flag XFUATU ≠ 0. If it is determined that there is no negative pressure request, the program is terminated as it is.

  On the other hand, if it is determined in step 202 that there is a negative pressure request, the process proceeds to step 203 where a target intake pipe pressure calculation program shown in FIG. After calculating (pipe negative pressure), the routine proceeds to step 204 where a target intake air amount calculation program of FIG. 5 described later is executed to calculate a target intake air amount MGA.

  Thereafter, the routine proceeds to step 205, where an intake pipe pressure control program of FIG. 6 described later is executed to calculate a target throttle opening degree that realizes the target intake pipe pressure MPM, and the actual throttle opening degree coincides with the target throttle opening degree. Thus, the throttle valve 16 is controlled to control the actual intake pipe pressure to the target intake pipe pressure MPM.

  Thereafter, the routine proceeds to step 206, where an intake air amount control program shown in FIG. 7 described later is executed to calculate a target intake valve closing timing for realizing the target intake air amount MGM. The electromagnetic actuator 30 is controlled so as to coincide with the valve closing timing, and the actual intake air amount is controlled to the target intake air amount MGA.

  Thereafter, the process proceeds to step 207, a target internal EGR correction amount calculation program of FIG. 8 described later is executed to calculate a target internal EGR correction amount MEGR, and then the process proceeds to step 208 to control internal EGR amount control of FIG. 9 described later. Execute the program to calculate the target correction amount of the intake valve opening timing (or valve overlap amount) that achieves the target internal EGR correction amount, and target the current intake valve opening timing (or valve overlap amount) The electromagnetic actuator 30 is controlled so that only the correction amount is corrected, and the change in the internal EGR amount is suppressed by correcting the decrease in the internal EGR amount by the increase in the internal EGR amount when switching from the normal control to the negative pressure control. To do.

  Thereafter, the routine proceeds to step 209, where the fuel injection amount and the injection timing are corrected according to the actual intake pipe pressure detected by the intake pipe pressure sensor 18 and the actual intake air temperature detected by the intake air temperature sensor (not shown). As a result, the fuel injection amount and the injection timing correspond to the change in the wet amount adhering to the inner wall of the intake port of the injected fuel according to the actual intake pipe pressure (actual intake pipe negative pressure) and the actual intake air temperature. Is corrected so that the amount of fuel supplied into the cylinder is substantially constant. The processing in step 209 serves as fuel injection amount correction means in the claims.

[Target intake pipe pressure calculation]
The target intake pipe pressure calculation program of FIG. 4 executed in step 203 of FIG. 3 serves as a target intake pipe pressure calculation means in the claims. When this program is started, first, in step 301, the target intake pipe pressure MPM is set to a predetermined negative pressure according to the item of the negative pressure request.

(1) When the negative pressure request flag XFUATU = 1, that is, in the case of a negative pressure request for starting (when the catalyst is inactive), the target intake pipe pressure MPM is set to a first predetermined negative pressure (for example, 70 kPa). Set.
(2) When the negative pressure request flag XFUATU = 2, that is, in the case of a negative pressure request for braking, the target intake pipe pressure MPM is set to a second predetermined negative pressure (for example, 60 kPa).

(3) When the negative pressure request flag XFUATU = 3, that is, in the case of a negative pressure request for purge control, the target intake pipe pressure MPM is set to a third predetermined negative pressure (for example, 90 kPa).
(4) When the negative pressure request flag XFUATU = 4, that is, in the case of other negative pressure requests (for example, for fault diagnosis), the target intake pipe pressure MPM is set to a fourth predetermined negative pressure (for example, 95 kPa). .

[Target intake air volume calculation]
The target intake air amount calculation program of FIG. 5 executed in step 204 of FIG. 3 serves as target intake air amount calculation means in the claims. When this program is started, first, in step 401, a required torque corresponding to the accelerator opening and the vehicle speed (or engine speed) is calculated using a map or a mathematical expression. Thereafter, the process proceeds to step 402, and the target intake air amount MGA corresponding to the required torque is calculated by a map or a mathematical expression.

  Here, the map of the required torque and the map of the target intake air amount MGA are respectively the same maps as those used during normal control. Thus, the target intake air amount MGA is set so that the intake air amount is equal to that during normal control during negative pressure control in which the target intake pipe pressure MPM is set to a predetermined negative pressure.

[Intake pipe pressure control]
The intake pipe pressure control program of FIG. 6 executed in step 205 of FIG. 3 serves as an intake pipe pressure control means in the claims. When this program is started, first, at step 501, the target intake pipe pressure MPM obtained by the target intake pipe pressure calculation program of FIG. 4 is read.

  Thereafter, the process proceeds to step 502, and the cylinder intake air amount (volume flow rate) corresponding to the engine rotation speed is calculated by a map or a mathematical formula. Then, the process proceeds to step 503, where the cylinder intake air amount, the surge tank volume, and the target intake pipe pressure. A target throttle passage air amount (target value of the air amount passing through the throttle valve 16) corresponding to the MPM is calculated by a map or a mathematical expression.

  Thereafter, the process proceeds to step 504, and the target throttle opening corresponding to the target throttle passing air amount is calculated by a map or a mathematical expression. Thereby, the target throttle opening degree which implement | achieves the target intake pipe pressure MPM is set.

  Thereafter, the process proceeds to step 505, where the actual intake pipe pressure is controlled to the target intake pipe pressure MPM by controlling the throttle valve 16 (actuator 15) so that the actual throttle opening matches the target throttle opening. Ensure necessary intake pipe negative pressure.

[Intake air volume control]
The intake air amount control program of FIG. 7 executed in step 206 of FIG. 3 serves as the intake air amount control means in the claims. When this program is started, first, at step 601, the target intake air amount MGA obtained by the target intake air amount calculation program of FIG. 5 is read.

  Thereafter, the process proceeds to step 602, and the target intake valve closing timing corresponding to the target intake air amount MGA is calculated by a map or a mathematical expression. This target intake valve closing timing is set in consideration of the cylinder volume at the closing timing of the intake valve 28.

  Thereafter, the process proceeds to step 603, and an intake valve closing timing correction amount corresponding to the engine operating state (for example, engine rotation speed) is calculated by a map or a mathematical expression. The intake valve closing timing correction amount is set in consideration of a change in air filling efficiency due to a change in the engine operating state, inertia, resonance, and the like.

  Thereafter, the process proceeds to step 604, where the final target intake valve closing timing is obtained by adding the intake valve closing timing correction amount to the target intake valve closing timing. Thereby, the target intake valve closing timing for realizing the target intake air amount MGA is set.

  Thereafter, the process proceeds to step 605, where the electromagnetic actuator 30 is controlled so that the actual intake valve closing timing coincides with the target intake valve closing timing, and the actual intake air amount (actual cylinder charge air amount) is set to the target intake air. By controlling to the amount MGA, the required torque corresponding to the accelerator opening is secured.

[Target internal EGR correction amount calculation]
The target internal EGR correction amount calculation program of FIG. 8 executed in step 207 of FIG. 3 serves as a target internal EGR control amount calculation means in the claims. When this program is started, first, in step 701, based on the target intake air amount MGA and the operating state of the engine 11 and the vehicle (for example, engine speed, accelerator opening, vehicle speed, etc.), The internal EGR amount EGR1 is calculated.

  Thereafter, the routine proceeds to step 702, where the internal EGR amount EGR2 at the time of negative pressure control is determined based on the target intake pipe pressure MPM and the operating state of the engine 11 and the vehicle (for example, engine speed, accelerator opening, vehicle speed, etc.). calculate.

Thereafter, the process proceeds to step 703, where the difference between the internal EGR amount EGR2 at the time of negative pressure control and the internal EGR amount EGR1 at the time of normal control (that is, the increment of the internal EGR amount when switching from normal control to negative pressure control) is obtained. It is obtained and used as the target internal EGR correction amount MEGR.
MEGR = EGR2-EGR1
As a result, the target internal EGR correction amount MEGR is set so that the internal EGR amount is equal to that during normal control during negative pressure control in which the target intake pipe pressure MPM is set to a predetermined negative pressure.

[Internal EGR control]
The internal EGR amount control program of FIG. 9 executed in step 208 of FIG. 3 serves as the internal EGR amount control means in the claims. When this program is started, first, in step 801, the actual intake pipe pressure PMJ detected by the intake pipe pressure sensor 18 is read, and then the process proceeds to step 802, where the current actual intake pipe pressure PMJ is set to the target intake pipe pressure MPM. It is determined whether it is higher.

As a result, when it is determined that the actual intake pipe pressure PMJ is higher than the target intake pipe pressure MPM, the routine proceeds to step 803, where the target internal EGR correction amount MEGR obtained by the target internal EGR amount calculation program of FIG. Correct to the intake pipe pressure change.
MEGR = MEGR × PMJ / MPM

  On the other hand, if it is determined that the step actual intake pipe pressure PMJ is less than or equal to the target intake pipe pressure MPM, the process proceeds to step 804, where the target internal EGR amount MEGR (= EGR2-EGR1) is adopted as it is.

  Thereafter, the process proceeds to step 805, where the target correction amount of the intake valve opening timing (or valve overlap amount) corresponding to the target internal EGR correction amount MEGR is calculated using a map or a mathematical expression. As a result, the target of the intake valve opening timing (or valve overlap amount) for reducing the internal EGR amount by the target internal EGR correction amount MEGR (that is, the amount of increase in the internal EGR amount when switching from normal control to negative pressure control) is achieved. Set the correction amount.

  Thereafter, the process proceeds to step 806, where the electromagnetic actuator 30 is controlled to correct the current intake valve opening timing (or valve overlap amount) by the target correction amount, and the normal control is switched to the negative pressure control. By correcting the decrease in the internal EGR amount by the increase in the internal EGR amount, a change in the internal EGR amount is suppressed, and the combustion state during negative pressure control is improved.

  Thereafter, the process proceeds to step 807, where the deviation of the engine speed between 30 ° C. A for example is calculated as the engine speed fluctuation ΔNE, and the average value of the engine speed fluctuation ΔNE over a predetermined period is calculated as the average engine speed fluctuation ΔNE (ave). Calculate as

Thereafter, the routine proceeds to step 808, where it is determined whether or not the difference between the engine rotation fluctuation ΔNE and the average engine rotation fluctuation ΔNE (ave) is smaller than a predetermined value (−D1). As a result, when it is determined that the difference between the engine rotation fluctuation ΔNE and the average engine rotation fluctuation ΔNE (ave) is smaller than the predetermined value (−D1), the target internal EGR correction amount MEGR is small (that is, the internal EGR amount). Therefore, it is determined that a drop in engine rotation has occurred, and the routine proceeds to step 809, where the target internal EGR correction amount MEGR is increased by a predetermined amount EGRG.
MEGR = MEGR + EGRG

  On the other hand, if it is determined in step 808 that the difference between the engine rotation fluctuation ΔNE and the average engine rotation fluctuation ΔNE (ave) is greater than or equal to a predetermined value (−D1), the process proceeds to step 810 and the engine rotation fluctuation ΔNE is performed. And whether the difference between the average engine speed fluctuation ΔNE (ave) is larger than a predetermined value D2.

As a result, when it is determined that the difference between the engine rotation fluctuation ΔNE and the average engine rotation fluctuation ΔNE (ave) is larger than the predetermined value D2, the target internal EGR correction amount MEGR is large (that is, the internal EGR amount reduction correction). Therefore, it is determined that the engine speed has blown up, and the process proceeds to step 811 where the target internal EGR correction amount MEGR is reduced by a predetermined amount EGRZ.
MEGR = MEGR-EGRZ
The target internal EGR correction amount MEGR corrected in step 809 or 811 is stored as a learning value in a rewritable nonvolatile memory such as a backup RAM.

[Combustion state improvement]
The combustion state improvement program shown in FIG. 10 is executed at a predetermined cycle during engine operation, and serves as a combustion state improvement means in the claims. When this program is started, first, in step 901, whether or not there is a negative pressure request is determined by whether or not the negative pressure request flag XFUATU ≠ 0. If it is determined that there is no negative pressure request, the program is terminated as it is.

  On the other hand, if it is determined in step 901 that there is a negative pressure request, the process proceeds to step 902, where the deviation of the engine rotation speed between, for example, 30 ° C. is calculated as the engine rotation fluctuation ΔNE, The average value of the engine speed fluctuation ΔNE at is calculated as the average engine speed fluctuation ΔNE (ave).

  Thereafter, the process proceeds to step 903, where it is determined whether or not the difference between the engine rotation fluctuation ΔNE and the average engine rotation fluctuation ΔNE (ave) is smaller than a predetermined value (−tne1). The predetermined value (-tne1) is set to a value smaller than the predetermined value (-D1).

  As a result, if it is determined that the difference between the engine speed fluctuation ΔNE and the average engine speed fluctuation ΔNE (ave) is smaller than a predetermined value (−tne1), it is determined that an excessive drop in engine speed has occurred. In step 905, the combustion deterioration determination flag NENNG is set to “1” which means that the combustion state has deteriorated.

  On the other hand, if it is determined in step 903 that the difference between the engine rotation fluctuation ΔNE and the average engine rotation fluctuation ΔNE (ave) is greater than or equal to a predetermined value (−tne1), the routine proceeds to step 904, where the engine rotation fluctuation ΔNE is performed. And a difference between the average engine speed fluctuation ΔNE (ave) and the predetermined value tne2. The predetermined value tne2) is set to a value larger than the predetermined value D2.

  As a result, when it is determined that the difference between the engine rotation fluctuation ΔNE and the average engine rotation fluctuation ΔNE (ave) is larger than the predetermined value tne2, it is determined that an excessive increase (variation) in engine rotation has occurred. In step 905, the combustion deterioration determination flag NENNG is set to “1” which means that the combustion state has deteriorated.

  Thereafter, the process proceeds to step 906, where it is determined whether or not the current negative pressure request is a brake negative pressure request (whether or not the negative pressure request flag XFUATU = 2). If not, the process proceeds to step 907, and combustion state improvement control is executed. In this combustion state improvement control, for example, the negative pressure request flag XFUATU is forcibly reset to “0” meaning no negative pressure request, and the negative pressure control is stopped. Thus, the internal intake gas amount is reduced by correcting the target intake pipe pressure MPM so as to approach the atmospheric pressure, thereby improving the combustion state. Note that the combustion state may be improved by correcting the target internal EGR correction amount MEGR in the direction in which the internal EGR amount is decreased.

  On the other hand, it is determined in step 903 that the difference between the engine rotation fluctuation ΔNE and the average engine rotation fluctuation ΔNE (ave) is equal to or greater than a predetermined value (−tne1), and in step 904, the engine rotation fluctuation ΔNE When it is determined that the difference from the average engine rotation fluctuation ΔNE (ave) is equal to or less than the predetermined value tne2, the process proceeds to step 908, and the combustion deterioration determination flag NENNG is determined to indicate that the combustion state has not deteriorated. Reset (or maintain) to "0" to end this program.

  An execution example of the negative pressure control of the first embodiment described above will be described with reference to the time chart of FIG. While the vehicle is running, for example, at the time t1 when the brake booster internal pressure becomes higher than a predetermined value due to the brake operation, the negative pressure request flag XFUATU is turned on (XFUATU ≠ 0), and the negative pressure control is started.

  First, a target intake pipe pressure MPM is set according to a negative pressure request item (for example, a negative pressure request for braking), and the throttle opening is controlled so as to realize the target intake pipe pressure MPM. Thus, the actual intake pipe pressure can be controlled to the target intake pipe pressure MPM, and a necessary intake pipe negative pressure can be ensured.

  Further, the target intake air amount MGA is calculated based on the accelerator opening, the vehicle speed, and the like, and the intake valve closing timing is controlled so as to realize the target intake air amount MGA. As a result, the actual intake air amount (actual cylinder charge air amount) can be controlled to the target intake air amount MGA, and the required torque according to the accelerator opening can be secured.

  Further, a target internal EGR correction amount MEGR (increase in internal EGR amount when switching from normal control to negative pressure control) is calculated based on the target intake air amount MGA, target intake pipe pressure MPM, and the like, and this target internal EGR is calculated. The intake valve opening timing (or valve overlap amount) is controlled so as to realize the correction amount MEGR. As a result, the internal EGR amount can be corrected to decrease by an increase in the internal EGR amount when switching from the normal control to the negative pressure control, and the change in the internal EGR amount can be suppressed. The combustion state can be improved.

  Further, the fuel injection amount and the injection timing are corrected in response to changes in the wet amount of the injected fuel adhering to the inner wall of the intake port, etc., according to the actual intake pipe pressure and the actual intake air temperature. As a result, the amount of fuel supplied into the cylinder can be made substantially constant, and disturbance of the air-fuel ratio can be prevented.

  Thereafter, at time t2 when the internal pressure of the brake booster becomes equal to or lower than a predetermined value by the negative pressure control, the negative pressure request flag XFUATU is set to OFF (XFUATU = 0), and the negative pressure control is terminated.

  In the first embodiment described above, since the target intake pipe pressure MPM is calculated according to the negative pressure request item, the negative pressure request items (for example, the negative pressure request for brake and the negative pressure for purge control). For each pressure request, etc., an appropriate target intake pipe pressure MPM (target intake pipe negative pressure) can be set, and the required intake pipe negative pressure can be reliably ensured, and the intake pipe pressure can be ensured. Can be prevented from being reduced more than necessary, and adverse effects (for example, an increase in the amount of internal EGR) caused by excessive reduction in the intake pipe pressure can be prevented.

  Further, in the first embodiment, during negative pressure control, the target intake air amount MGA is calculated so that the intake air amount is equivalent to that during normal control, and the target internal EGR amount is equivalent to that during normal control. Since the internal EGR correction amount MEGR is calculated, even during negative pressure control, the same intake air amount and internal EGR amount as during normal control are ensured, and engine performance (torque and combustion state) equivalent to that during normal control is ensured. Can be demonstrated.

  Further, in the first embodiment, when the combustion state deteriorates during the negative pressure control, the target intake pipe pressure MPM is corrected so as to approach the atmospheric pressure (or by correcting the target internal EGR correction amount MEGR). Since the internal EGR amount is reduced to improve the combustion state, it is possible to prevent deterioration in drivability during negative pressure control.

Next, Embodiment 2 of the present invention will be described with reference to FIG.
In the first embodiment, the intake valve closing timing is controlled during negative pressure control to control the intake air amount to the target intake air amount MGA. However, the variable valve lift device that varies the lift amount of the intake valve 28 ( In the case of a system equipped with an unillustrated), as in the second embodiment, the intake valve lift amount may be controlled during negative pressure control to control the intake air amount to the target intake air amount MGA. .

  The processing contents of the intake air amount control program of FIG. 12 executed by the ECU 27 in the second embodiment will be described below. When this program is started, first, in step 1001, the target intake air amount MGA obtained by the target intake air amount calculation program of FIG. 5 is read.

  Thereafter, the process proceeds to step 1002, and a target intake valve lift amount corresponding to the target intake air amount MGA is calculated by a map or a mathematical expression. This target intake valve lift amount is set in consideration of the cylinder volume at the closing timing of the intake valve 28.

  In the next step 1003, an intake valve lift correction amount corresponding to the engine operating state (for example, engine rotation speed) is calculated using a map or a mathematical expression. This intake valve lift correction amount is set in consideration of a change in air filling efficiency due to a change in engine operating state, inertia, resonance, and the like.

  Thereafter, the process proceeds to step 1004, and the final target intake valve lift amount is obtained by adding the intake valve lift correction amount to the target intake valve lift amount. Thus, a target intake valve lift amount that realizes the target intake air amount MGA is set.

  Thereafter, the routine proceeds to step 1005, where the variable valve lift device is controlled so that the actual intake valve lift amount matches the target intake valve lift amount, and the actual intake air amount (actual cylinder charge air amount) is set to the target intake air amount. By controlling to the required torque, the required torque according to the accelerator opening is ensured.

Also in the second embodiment described above, the same effect as in the first embodiment can be obtained.
In the first and second embodiments, the present invention is applied to a system that controls the intake air amount by changing the valve closing timing or the lift amount of the intake valve 28. However, the present invention is not limited to this. A system for controlling the intake air amount by changing one or more of valve opening / closing characteristics (valve opening timing, valve closing timing, lift amount, valve opening period, etc.), and both intake and exhaust valves 28 and 29 The present invention may be applied to a system that controls the intake air amount by varying one or more of the valve opening / closing characteristics.

It is a schematic block diagram of the whole engine control system in Example 1 of this invention. It is a flowchart which shows the flow of a process of the negative pressure request | requirement determination program of Example 1. FIG. It is a flowchart which shows the flow of a process of the negative pressure control program of Example 1. FIG. 6 is a flowchart illustrating a processing flow of a target intake pipe pressure calculation program according to the first embodiment. It is a flowchart which shows the flow of a process of the target intake air amount calculation program of Example 1. FIG. 6 is a flowchart illustrating a processing flow of an intake pipe pressure control program according to the first embodiment. 6 is a flowchart illustrating a process flow of an intake air amount control program according to the first embodiment. 6 is a flowchart illustrating a processing flow of a target internal EGR correction amount calculation program according to the first embodiment. 6 is a flowchart illustrating a flow of processing of an internal EGR amount control program according to the first embodiment. It is a flowchart which shows the flow of a process of the combustion condition improvement program of Example 1. FIG. 3 is a time chart illustrating an execution example of negative pressure control according to the first embodiment. It is a flowchart which shows the flow of a process of the intake air amount control program of Example 2. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 16 ... Throttle valve, 20 ... Fuel injection valve, 21 ... Spark plug, 22 ... Exhaust pipe, 27 ... ECU (Target intake air amount calculation means, Target intake pipe pressure calculation) Means, target internal EGR control amount calculation means, intake air amount control means, intake pipe pressure control means, internal EGR amount control means, fuel injection amount correction means, combustion state improvement means), 28 ... intake valve, 29 ... exhaust valve, 30, 31 ... Electromagnetic actuator (variable valve device), 37 ... Evaporative fuel processing device, 39 ... Brake booster

Claims (11)

In a control device for an internal combustion engine comprising a variable valve device capable of controlling at least an intake air amount by varying valve opening / closing characteristics of both intake valves and intake / exhaust valves of the internal combustion engine,
A target intake air amount calculating means for calculating a target intake air amount based on the operating state of the internal combustion engine and / or the vehicle;
Target intake pipe pressure calculating means for calculating a target intake pipe pressure based on the operating state of the internal combustion engine and / or the vehicle;
Target internal EGR control amount calculation means for calculating a target control amount of the in-cylinder exhaust gas residual amount (hereinafter referred to as “target internal EGR control amount”) based on the operating state of the internal combustion engine and / or the vehicle;
Intake air amount control means for controlling the intake air amount so as to realize the target intake air amount;
An intake pipe pressure control means for controlling the intake pipe pressure so as to realize the target intake pipe pressure;
A control device for an internal combustion engine, comprising: internal EGR amount control means for controlling a cylinder exhaust gas residual amount (hereinafter referred to as "internal EGR amount") so as to realize the target internal EGR control amount.   The intake air amount control means controls the intake air amount by controlling at least one of a closing timing and a lift amount of the intake valve based on the target intake air amount. The internal combustion engine control device described.   The control apparatus for an internal combustion engine according to claim 1 or 2, wherein the intake pipe pressure control means controls the intake pipe pressure by controlling a throttle opening based on the target intake pipe pressure.   The internal EGR amount control means controls the internal EGR amount by controlling at least one of a valve opening timing and a valve overlap amount of the intake valve based on the target internal EGR control amount. Item 4. The control device for an internal combustion engine according to any one of Items 1 to 3.   The target intake pipe pressure calculating means calculates the target intake pipe pressure according to an item of the negative pressure request when a negative pressure request requiring the intake pipe negative pressure is generated. The control device for an internal combustion engine according to any one of claims 1 to 4.   The target intake air amount calculating means sets the target intake air amount so that the intake air amount is equivalent to that during normal control during negative pressure control in which the target intake pipe pressure is set to a predetermined negative pressure. The control device for an internal combustion engine according to any one of claims 1 to 5.   The target internal EGR control amount calculation means sets the target internal EGR control amount so that the internal EGR amount becomes equal to that during normal control when the target intake pipe pressure is set to a predetermined negative pressure. The control device for an internal combustion engine according to any one of claims 1 to 6, wherein   2. A fuel injection amount correcting means for correcting a fuel injection amount in accordance with an actual intake pipe pressure during negative pressure control in which the target intake pipe pressure is set to a predetermined negative pressure. The control apparatus for an internal combustion engine according to any one of claims 7 to 9.   When the combustion state deteriorates during negative pressure control in which the target intake pipe pressure is set to a predetermined negative pressure, the target internal EGR control amount and / or the target intake pipe pressure are set so that the combustion state is improved. 9. The control apparatus for an internal combustion engine according to claim 1, further comprising combustion state improving means for correcting.   The combustion state improving means improves the combustion state by correcting the target internal EGR control amount in a direction in which the internal EGR amount is reduced when the combustion state deteriorates during the negative pressure control. The control device for an internal combustion engine according to claim 9.   The combustion state improving means improves the combustion state by correcting the target intake pipe pressure in a direction in which the intake pipe pressure approaches the atmospheric pressure when the combustion state deteriorates during the negative pressure control. The control device for an internal combustion engine according to claim 9 or 10.

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